Multimedia data may include metadata being data about data. Metadata is a special kind of data, which is linked to other data called essence. Metadata is typically used as index message for essence. Essence is the basic data, such as text essence, picture essence, video essence, or audio essence.
The metadata structure is essentially characterized by two parts: metadata-essence (MD-essence) and metadata-link (MD-link). MD-essence is part of a metadata, which is designed to be human-perceptible, and which serves as the proxy by which the metadata will be presented to the user in any user interface of systems employing metadata. MD-link is part of the metadata, which links to any kind of essence.
A way how to generate efficient metadata is always an important issue for metadata applications. A possible way for generating metadata is to convert essence into metadata. In practice, some essence, such as text essence or thumbnail picture essence, contains a lot of compact information which can be utilized for metadata. Usually, content of essence can be converted directly into metadata essence. However, it is a problem to generate MD-link data conveniently in case of conversion of essence into metadata.